Debarking process and apparatus

ABSTRACT

Debarking method and apparatus wherein limb sections to be debarked and a plurality of smaller, substantially higher density objects are disposed in a vaned chamber which is rotated about a horizontal axis. The high density objects are thereby caused to randomly impact the surface of the limb sections to separate the bark from the wood.

United States Patent [191 Smiltneek [451 July 17, 1973 DEBARKING PROCESS AND APPARATUS [76] Inventor: Ralmond J. Smiltneek, PO. Box 273, Butler, Wis. 53007 221 Filed: Aug. 31, 1971 211 App]. No.: 176,615

[52] US. Cl. 144/208 B, 144/311 [51] Int. Cl B271 2/00 [58] Field of Search 144/208 B, 208 R, 144/31 1 [56] References Cited UNITED STATES PATENTS 1,700,390 1/1929 Ullgren 144/208 B FOREIGN PATENTS OR APPLICATIONS 68,393 11/1929 Sweden 144/208 B 1,179,697 10/1964 Germany 144/2011 ll Primary ExaminerDonald R. Schran Attorney-Ralph G. Hohenfeldt and Fred Wiviott [5 7] ABSTRACT Debarking method and apparatus wherein limb sections to be debarked and a plurality of smaller, substantially higher density objects are disposed in a vaned chamber which is rotated about a horizontal axis. The high density objects are thereby caused to randomly impact the surface of the limb sections to separate the bark from the wood.

18 Claims, 4 Drawing Figures Patented Jul 17, 1973 FIG. I

INVENTOR RALMOND J. SMILTNEEK BY) t BACKGROUND OF THE INVENTION This invention relates to method and apparatus for debarking limb sections.

There is a substantial need for fuller utilization of pulpwood in view of increasing demand and resource limitations. At present, processing losses may account for up to 70 percent of a tree cut.These losses result to a substantial degree because heretofore it has not been practical to utilize tree limbs and tops because no efficient and economic debarking method and apparatus has been available. In the pulp and paper industry efficient bark removal was especially important because only small quantities of bark can be tolerated in the pulp mixture. For example, approximately 4 percent is the upper limit of bark content that will be accepted by pulp mills. There have been a number of attempts to debark limbs and tree tops by first chipping and then storage and compression or air flotation methods. These methods, however, have not been wholly satisfactory so that at present these tree portions are generally left at the cutting site to rot.

SUMMARY OF THE INVENTION It is a general object of the invention to provide a new and improved debarking method and apparatus.

Another object of the invention is to provide a debarking apparatus particularly adapted to debark tree limbs and top sections.

A further object of the invention is to provide a debarking apparatus which does not result in a substantial loss of wood fiber.

Yet another object of the invention is to provide a debarking apparatus which may be employed at the cutting site.

A still further object of the invention is to provide a debarking apparatus and method which is not dependent upon the shape of the tree segments being debarked.

These and other objects and advantages of the instant invention will become more apparent from the detailed descriptions thereof taken with the accompanying drawings.

In general terms the invention comprises a method and apparatus for randomly impacting the wood segments being debarked with objects having a substantially higher density than the wood.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view of the apparatus according to a preferred embodiment of the present invention;

FIG. 2 is a top plan view of the apparatus illustrated in FIG. 1;

FIG. 3 is a side elevational view of a portion of the apparatus shown in FIG. I; and

FIG. 4 is a view taken along lines 4-4 of FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIGS. 1 and 2 illustrate the preferred embodiment of the instant invention to include a hollow separating chamber which is open at a first end 1 I for receiving a charge of tree limb and top sections to be debarked. As will be described more fully below, the chamber 10 is mounted for rotation about a substantially horizontal axis for randomly moving an impact medium into ran dom impacting engagement with the wood sections to be debarked. An air separating system 12 and a baffle 13 coact to remove the bark sections from the separating chamber 110. Any suitable means, such as a water separator 114 may be employed for separating the debarked wood segments from the impacting medium.

The separating chamber 10 is shown more specifically in FIGS. 3 and 4 to comprise an outer shell having a pair of frustoconical end sections 20 and 21 joined by a center cylindrical section 22. The small diameter end of section 21 mates with a smaller, fixedly mounted frustoconical section 23. As indicated previously, the end 11 of the section 20 is open for receiving and discharging the wood sections and impacting media while end 24 of section 23 is open discharging bark, leaves, twigs and other tree material freed in separating chamber 10.

A plurality of longitudinally extending vanes are suitably mounted on the interior of the chamber 10 for circulating the wood pieces 26 which are to be debarked and a plurality of impacting objects 28. The baffle 13 is fixedly mounted within chamber 10 and extends longitudinally therein and is generally disposed to one side of and inclined relative to a vertical plane containing the longitudinal axis of chamber 10. The configuration of the housing sections 21 and 22 are such that the wood sections 26 and the impacting members 28 tend to be concentrated in the central section 22 and the larger diameter portions of sections 20 and 21. The baffle 13 is spaced from the walls of the chamber 10 to permit passage of the vanes 25 as chamber 10 rotates with a greater separation existing between the lower end of the baffle and the walls of chamber 10 while the right end of baffle 13 is viewed in FIG. 3 is fixed to section 23.

As seen in FIG. 4, the chamber 10 is mounted for counterclockwise rotation about its longitudinal axis in any suitable manner such as by friction wheels 30 which engage the cylindrical central section 22. The wheels 30 may each be mounted on an individual shaft 31 supported for rotation on bearings 32 and which may be driven from a motor (not shown) coupled by a belt (not shown) to a pulley 33 suitably affixed to shaft 31.

In performance of the process, a charge of wood sections 26 and impacting members 28 are initially fed into the end ll of chamber 10 and the chamber is then rotated. The wood sections 26 and impacting objects 28 are thereby circulated by the vanes 25 upwardly and toward the center of the chamber. It will be appreciated that the height to which the particles are raised within the chamber 10 will to some extent be deteremined by the speed of rotation. It will be appreciated therefore that the speed of chamber it) should be sufficiently great to carry these objects to the upper end of the chamber but less than the critical centrifugal speed which would tend to hold the objects 26 and 28 against the surface of chamber W. About percent of this critical speed has been found to be satisfactory.

The impacting objects 28 should generally have a density several times greater than the wood pieces 26 being debarked and are preferably substantially smaller in size. Although both the impacting objects 28 and the wood sections 26 may move through the same general pathway, virtually all the work of debarking is delivered by the impacting objects 28 because of their relatively high density relative to the wood. Each piece of wood receives generally uniformly and randomly distributed surface impacts and abrasions from the impacting objects 28. If the unit impact energy lies above a critical level, determined by wood specie and condition, the gradual and uniform degrading of the bark structure occurs, whereby the bond between the bark and the wood is uniformly weakened and the bark is soon stripped away. For many species of wood there is a definite difference between the bark breakdown energy and the wood breakdown energy. If the chamber is operated somewhere between these two critical energy levels, a suitably rapid destruction of the bark will occur, with relatively little damage into the wood.

Because this process exposes the surface of the wood pieces to a uniformly distributed energy delivery, the roundness and symmetry of the wood is not important, and shape becomes relatively insignificant. irregularly shaped pieces of wood are efficiently debarked with very little loss of wood fiber. Effective debarking can therefore be achieved regardless of the sizes and shapes of the tree sections available or the apparatus for cutting these sections. A practical wood section length is about 12 to 24 inches although lengths shorter or longer may also be employed. Similarly the cross sectional dimension of the wood can vary widely but preferably the sections should be in the range of two to six inches. The apparatus for the cutting of the sections into the desired lengths has not been shown but any apparatus suitable for this purpose may be employed.

Theaction within the chamber 10 is mainly selective abrading, crushing and shearing the bark in preference to the wood fiber. This preferential action is enhanced by the fact that most bark is normally more brittle than the wood it is associated with and hence more susceptible to impact crushing.

The size, shape, hardness and energy level of the impacting objects may vary widely. Examples of impacting objects which were found to be satisfactory were mild steel slugs having generally cubicle, cylindrical or disc-like shapes about a cubic inch in volume. These were employed in a rotating chamber of approximately six feet in diameter at about 80 percent of critical speed and were found to be effective for rapidly abrading and removing bark from three inch diameter aspen wood. Also, typical ceramic or metallic materials used in ball mills or even stones can be employed. It will be understood that the terms stones as used herein means both natural stones and crushed rock.

As indicated above the air separating system 12 is provided to separate bark as it is being removed from thewood sections 26. Toward this end, the system 12 is shown inFIGS. l and 2 to include a fan 40, coupled by athroat 41, to the stationary chamber portion 24. Fan 40 draws air inwardly of the chamber 10 through opening 11. A pivotable valve plate 42 which. normally extends from bafi'le l3 and across stationary chamber section 23, causes the air to flow around the lower end of baffle 13 at the point where the impact members 28 strike the limb sections 26 and wherein separation of the bark from the sections is most likely to occur. This air stream not only carries the separated bark but also twigs, leaves and dirt that may be released in the debarking process.

it may be desireable to employ the bark removed from the wood sections for further processing. Toward this end the valve plate 42 is initially in its closed position shown in FIG. 2 to effect the immediate removal of small twigs and leaves. The valve plate 42 is then opened and/or the fan 40 is turned off so that the bark segments remain in chamber 10. The objects 28 will then grind the bark into small particles which may then be removed in the normal manner.

The bark and other waste material may be separated from the air stream in any suitable manner. For example, the fan 40 may be coupled by a chute 43 to a large particle separator 44 for collecting the larger bark segments. A second chute 45 may couple the separator 44 to a cyclone separator 46 wherein the smaller particles are separated and collected in a bin 47 while the clean air stream is discharged from stack 48.

After the wood sections 26 have been debarked, they may be separated from the impacting members 28 in any suitable manner such as by dumping the contents of the chamber 10 into a flotation separator 14. in addition any wood members which may still contain bark can also be returned to separator 10. While a flotation separator has been shown, those skilled in the art will appreciate that other separation apparatus such as, magnetic separtors or screening, for example, may be employed. 7

The debarked wood produced in the process will generally be sufficiently clean for chipping into wood pulps or flaking for particle board use. The process provides an efiicient and economical method for debarking limbs and treetop sections which are normally now discarded. This not only provides an economical use for tree sections which have heretofore been discarded,

' but also allows the use of trees which were heretofore not usable because of size or shape.

Those skilled in the art will appreciate that the apparatus and method according to the invention may also be applied for the removal of any undesired matter from wood sections. For example, plaster could be removed from wood salvaged from demolished buildings, rot could be removed from log sections and bark from sawmill slabs. Also whole logs could be debarked by merely modifying vanes 25 so that the log rotated whereby the impact objects 28 could randomly engage its surface.

While only a single embodiment of the invention has been shown and described, wherein both the wood sections and impacting objects were moved simulta neously in a single chamber. The inventive concept could also be carried out by any system wherein the impacting objects would be imparted with energy for crushing and abrading the bark. Also, while the invention is discussed with respect to a batch process, continuous flow of wood sections and/or impact objects are also contemplated. Accordingly, it is not intended that the invention be limited to the foregoing description but only by the scope of the appended claims.

I claim:

1. An apparatus for debarking wood sections comprising:

a plurality of unconnected impact means each having a higher specific gravity than said wood sections, first means defining an impact zone for containing said sections and said plurality of impact means, the dimensions of said impact zone being at least several times greater than the corresponding dimensions of said wood sections and said impact means to permit relatively free movement of said sections and said impact means within said impact zone,

and second means for moving said plurality of impact means within said impact zone a distance substantially greater than the largest dimension of said impact means and said wood sections for random impacting engagement with said wood sections whereby the bark on said sections is removed.

2. The apparatus set forth in claim 1 wherein said impact means comprises a plurality of objects having a smaller size than said wood sections.

3. The apparatus set forth in claim 1 wherein said first means comprises achamber means and said second means includes means for rotating said chamber means about a substantially horizontal axis.

4. The apparatus set forth in claim 3 wherein said second means also includes means formed on the inner surface of said chamber for engaging said objects to impart energy thereto for impacting said wood sections.

5. Apparatus for debarking wood sections comprismg:

a plurality of unconnected impact means each having a higher specific gravity than said wood sections, chamber means for containing said sections and said plurality of impact means, means for rotating said chamber means about a substantially horizontal axis and means formed on the inner surface of said chamber means for engaging said impact means to move the same and impart energy thereto for impacting said wood sections whereby the bark on said sections is removed,

baffle means extending longitudinally along said chamber means, said impact means and wood sections being disposed on one side of said baffle means,

an exit opening formed in said chamber means on the other side of said bafi'le means,

and means for creating an air stream on said one side of said baffle means and outwardly of said opening.

6. The apparatus set forth in claim 5 wherein said impact means comprises a plurality of objects having a smaller size than said wood sections.

7 A method for removing undesirable material from wood sections comprising the steps of:

providing an impact zone,

placing in said impact zone a plurality of unconnected impact means having a higher specific gravity than the wood sections to be debarked, introducing into said impact zone at least one of said wood sections,

the dimensions of said impact zone being at least several times greater than each of the corresponding dimensions of said impact means and wood sections to permit relatively free movement of said impact means and said wood section within said zone, continuously separating said impact means and said wood section,

and randomly moving said plurality of impact means relative to said wood section and into impacting engagement therewith.

8. The method set forth in claim 7 wherein said undesirable material comprises bark, said impact means comprises a plurality of individual objects, and including the steps of containing a plurality of said sections in said zone, and moving said objects along a path whose length is at least several times greater than the largest dimension of said objects.

9. The method set forth in claim 8 and including the step of providing impact objects having a substantially smaller size than said wood sections.

10. The method set forth in claim 9 and including the step of imparting said objects with energy and releasing said objects for random engagement with said wood sections.

11. The method set forth in claim 10 wherein said impacting zone comprises chamber means and rotating said chamber means about a substantially horizontal axis for moving said impact objects into engagement with said wood sections.

12. The method set forth in claim 11 and including the step of rotating said chamber at a rate sufficient to raise said objects above said substantially horizontal axis prior to release.

13. The method set forth in claim 12 and including the step of providing said chamber with object engaging means for carrying said objects above said substantially horizontal axis.

14. The method set forth in claim 13 wherein said objects comprise a metallic material.

15. The method set forth in claim 13 wherein said objects comprise a ceramic material.

16. The method set forth in claim 13 wherein said objects comprise stones.

17. The method set forth in claim 13 and including the step of removing separated bark from said impacting zone.

18. A method for debarking wood sections comprising the steps of:

containing in a chamber a plurality of wood sections and a plurality of impact objects, said objects having a higher specific gravity and smaller in size than said wood sections, said chamber including means for carrying said objects upwardly upon rotation of said chamber,

rotating said chamber means about a substantially horizontal axis and at a rate sufficient to raise said objects above said substantially horizontal axis for moving said objects into random impacting engagement with said wood sections,

and inducing an air stream through said impacting zone to remove separated bark therefrom.

i I! t 8 i 

1. An apparatus for debarking wood sections comprising: a plurality of unconnected impact means each having a higher specific gravity than said wood sections, first means defining an impact zone for containing said sections and said plurality of impact means, the dimensions of said impact zone being at least several times greater than the corresponding dimensions of said wood sections and said impact means to permit relatively free movement of said sections and said impact means within said impact zone, and second means for moving said plurality of impact means within said impact zone a distance substantially greater than the largest dimension of said impact means and said wood sections for random impacting engagement with said wood sections whereby the bark on said sections is removed.
 2. The apparatus set forth in claim 1 wherein said impact means comprises a plurality of objects having a smaller size than said wood sections.
 3. The apparatus set forth in claim 1 wherein said first means comprises a chamber means and said second means includes means for rotating said chamber means about a substantially horizontal axis.
 4. The apparatus set forth in claim 3 wherein said second means also includes means formed on the inner surface of said chamber for engaging said objects to impart energy thereto for impacting said wood sections.
 5. Apparatus for debarking wood sections comprising: a plurality of unconnected impact means each having a higher specific gravity than said wood sections, chamber means for containing said sections and said plurality of impact means, means for rotating said chamber means about a substantially horizontal axis and means formed on the inner surface of said chamber means for engaging said impact means to move the same and impart energy thereto for impacting said wood sections whereby the bark on said sections is removed, baffle means extending longitudinally along said chamber means, said impact means and wood sections being disposed on one side of said baffle means, an exit opening formed in said chamber means on the other side of said baffle means, and means for creating an air stream on said one side of said baffle means and outwardly of said opening.
 6. The apparatus set forth in claim 5 wherein said impact means comprises a plurality of objects having a smaller size than said wood sections.
 7. A method for removing undesirable material from wood sections comprising the steps of: providing an impact zone, placing iN said impact zone a plurality of unconnected impact means having a higher specific gravity than the wood sections to be debarked, introducing into said impact zone at least one of said wood sections, the dimensions of said impact zone being at least several times greater than each of the corresponding dimensions of said impact means and wood sections to permit relatively free movement of said impact means and said wood section within said zone, continuously separating said impact means and said wood section, and randomly moving said plurality of impact means relative to said wood section and into impacting engagement therewith.
 8. The method set forth in claim 7 wherein said undesirable material comprises bark, said impact means comprises a plurality of individual objects, and including the steps of containing a plurality of said sections in said zone, and moving said objects along a path whose length is at least several times greater than the largest dimension of said objects.
 9. The method set forth in claim 8 and including the step of providing impact objects having a substantially smaller size than said wood sections.
 10. The method set forth in claim 9 and including the step of imparting said objects with energy and releasing said objects for random engagement with said wood sections.
 11. The method set forth in claim 10 wherein said impacting zone comprises chamber means and rotating said chamber means about a substantially horizontal axis for moving said impact objects into engagement with said wood sections.
 12. The method set forth in claim 11 and including the step of rotating said chamber at a rate sufficient to raise said objects above said substantially horizontal axis prior to release.
 13. The method set forth in claim 12 and including the step of providing said chamber with object engaging means for carrying said objects above said substantially horizontal axis.
 14. The method set forth in claim 13 wherein said objects comprise a metallic material.
 15. The method set forth in claim 13 wherein said objects comprise a ceramic material.
 16. The method set forth in claim 13 wherein said objects comprise stones.
 17. The method set forth in claim 13 and including the step of removing separated bark from said impacting zone.
 18. A method for debarking wood sections comprising the steps of: containing in a chamber a plurality of wood sections and a plurality of impact objects, said objects having a higher specific gravity and smaller in size than said wood sections, said chamber including means for carrying said objects upwardly upon rotation of said chamber, rotating said chamber means about a substantially horizontal axis and at a rate sufficient to raise said objects above said substantially horizontal axis for moving said objects into random impacting engagement with said wood sections, and inducing an air stream through said impacting zone to remove separated bark therefrom. 